Sensor identification

ABSTRACT

Techniques described here use variations in the sensor to generate an identifier for the sensor. Each sensor may be comprised of sub-sensing units, called pixels that may demonstrate variation in their sensing capability from one pixel to another. Embodiments of the invention, describe a method for using the relative variance of each pixel (relative to the whole sensor or/and a portion of the sensor) in generating an identifier for the sensor. In one embodiment, the method may obtain information associated with a plurality of pixels from a sensor, detect variations in the information associated for each of the pixels from a subset of the plurality of pixels and generate an identifier for the sensor using the detected variations in the information associated with each of the pixels from the subset of plurality of pixels.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a non-provisional application and claims the benefitof priority of U.S. Provisional Application No. 61/926,037 titled“SENSOR IDENTIFICATION,” and filed on Jan. 14, 2014, which is hereinincorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The present disclosures generally relate to generating identifiers, andmore specifically, generating unique identifiers for sensors.

BACKGROUND

Sensors detect physical input and in some instances convert the physicalinput to electrical or optical output. The electrical output may be usedby a device hosting the sensor in a variety of ways. Applications ofsensors are widespread and sensors are used in everyday devices, such asmobile devices. Some examples of sensors may include inertial sensors,imaging sensors, chemical sensors, biometric sensors, ultrasonicsensors, etc. Ultrasonic sensors may operate by interpreting the echoesfrom radio or sound waves. For instance, ultrasonic sensors may generatehigh frequency sound waves and evaluate the echo which is received backby the sensor. In some implementations, ultrasonic sensors calculate thetime interval between sending the signal and receiving the echo todetermine the distance to an incident surface. In some instances, theultrasonic sensors may also operate in a passive mode by detectingambient signals from the environment. One application of ultrasonicsensors may include detecting fingerprints of a user for authenticatingthe user.

In some instances, uniquely identifying the sensor may increase oraugment the security of the authentication process. In some instances,uniquely identifying the sensor may allow systems, remote servers,clouds, applications and programs in improving security and also enableforensics in instances of security breaches.

BRIEF SUMMARY

Techniques described herein provide a method for generating anidentifier, and more specifically, generating unique identifiers forsensors.

In some aspects, the identifier for the sensor uniquely (or uniquelywithin an acceptable degree) identifies the sensor. In some instances,uniquely identifying the sensor may aid in increasing or augmenting thesecurity of the authentication process. In some instances, uniquelyidentifying the sensor may allow systems, remote servers, clouds,applications and programs in improving security and also enableforensics in instances of security breaches.

In some instances, uniquely identifying the sensor may increase oraugment the security of the authentication process. Some currentsolutions provide fixed identifiers, in some instances, etched into thesensor. However, these identifiers are inflexible; are expensive toimplement; can be faked, masked, changed or stolen; and do not provide acost effective and robust method for uniquely identifying a sensor.

In certain aspects, techniques describe a method for generating anidentifier for the sensor using intrinsic properties of the sensor.Described techniques allow generation of an identifier in a costeffective manner using spatially temporal and global information fromthe sensor that is robust against contrast variations, input signalvariations, and gradual changes of sensor characteristics. Furthermore,techniques described allow for using an identifier for a sensor even ininstances where the sensors may have spatial and temporal defects anddegradations.

In an example method for generating an identifier for a sensor, themethod may include accessing, by a computing device, sensed informationfor each pixel from a plurality of pixels of the sensor for an at leastone sensing environment, determining, by the computing device, a firstvariance representing a variation in the sensed information for a firstsubset of the plurality of pixels using the sensed information for eachpixel from the first subset of the plurality of pixels of the sensor,determining, by the computing device, a second variance representing avariation in the sensed information for a second subset of the pluralityof pixels using the sensed information for each pixel from the secondsubset of the plurality of pixels of the sensor, wherein the firstsubset of the plurality of pixels is different from the second subset ofthe plurality of pixels, determining, by the computing device, a pixelidentifier value for each pixel from a third subset of the plurality ofpixels by comparing the sensed information for each pixel from the thirdsubset of the plurality of pixels with the first variance and the secondvariance, and generating, by the computing device, the identifier usingthe pixel identifier values for each of the plurality of pixels from thethird subset of the plurality of pixels.

In one aspect of the method, the plurality of pixels from the thirdsubset may also belong to the first subset and the second subset. Incertain aspects, the plurality of pixels from the second subset may alsobelong to the first subset.

In one aspect of the method, the method further comprises determiningthe pixel identifier value for each pixel from the third subset of theplurality of pixels by receiving the sensed information for a pluralityof sensing environments. For example, the sensing environments mayinclude bias current enabled, bias current disabled, bias currentshifted, tone burst enabled, or tone burst disabled.

In one aspect of the method, generating the identifier value may includeconcatenating the pixel identifier values for the plurality of pixelsfrom the third subset of the plurality of pixels. In someimplementations, the plurality of pixels belonging to the second subsetis received by the computing device coupled to the sensor from a remotedevice.

In certain aspects, the sensor may be an image sensor or an ultrasonicsensor. In some aspects, the sensor may be an ultrasonic fingerprintsensor. In some instances, the sensor may be used for authenticating auser using biometric information.

According to certain aspects, an example device for generating anidentifier for a sensor may include the sensor coupled to the device,the sensor comprising a plurality of pixels configured to senseinformation, a memory, and a processor coupled to the memory. Theprocessor may be configured to receive the sensed information for eachpixel from the plurality of pixels of the sensor for an at least onesensing environment, determine a first variance representing a variationin the sensed information for a first subset of the plurality of pixelsusing the sensed information for each pixel from the first subset of theplurality of pixels of the sensor, determine a second variancerepresenting a variation in the sensed information for a second subsetof the plurality of pixels using the sensed information for each pixelfrom the second subset of the plurality of pixels of the sensor, whereinthe first subset of the plurality of pixels is different from the secondsubset of the plurality of pixels, determine a pixel identifier valuefor each pixel from a third subset of the plurality of pixels bycomparing the sensed information for each pixel from the third subset ofthe plurality of pixels with the first variance and the second variance,and generate the identifier using the pixel identifier values for eachof the plurality of pixels from the third subset of the plurality ofpixels.

In one aspect of the example device, the plurality of pixels from thethird subset may also belong to the first subset and the second subset.In certain aspects, the plurality of pixels from the second subset mayalso belong to the first subset.

In one aspect of the example device, the method further comprisesdetermining the pixel identifier value for each pixel from the thirdsubset of the plurality of pixels by receiving the sensed informationfor a plurality of sensing environments. For example, the sensingenvironments may include bias current enabled, bias current disabled,bias current shifted, tone burst enabled, or tone burst disabled.

In one aspect of the example device, generating the identifier value mayinclude concatenating the pixel identifier values for the plurality ofpixels from the third subset of the plurality of pixels. In someimplementations, the plurality of pixels belonging to the second subsetis received by the device coupled to the sensor from a remote device.

In certain aspects, the sensor may be an image sensor or an ultrasonicsensor. In some aspects, the sensor may be an ultrasonic fingerprintsensor. In some instances, the sensor may be used for authenticating auser using biometric information.

In an example non-transitory computer-readable storage medium, whereinthe non-transitory computer-readable storage medium comprisesinstructions executable by a processor, the instructions may includeinstructions to receive sensed information for each pixel from aplurality of pixels of a sensor for an at least one sensing environment,determine a first variance representing a variation in the sensedinformation for a first subset of the plurality of pixels using thesensed information for each pixel from the first subset of the pluralityof pixels of the sensor, determine a second variance representing avariation in the sensed information for a second subset of the pluralityof pixels using the sensed information for each pixel from the secondsubset of the plurality of pixels of the sensor, wherein the firstsubset of the plurality of pixels is different from the second subset ofthe plurality of pixels, determine a pixel identifier value for eachpixel from a third subset of the plurality of pixels by comparing thesensed information for each pixel from the third subset of the pluralityof pixels with the first variance and the second variance, and generatethe identifier using the pixel identifier values for each of theplurality of pixels from the third subset of the plurality of pixels.

In one aspect of the non-transitory computer-readable storage medium,the plurality of pixels from the third subset may also belong to thefirst subset and the second subset. In one aspect of the non-transitorycomputer-readable storage medium, the plurality of pixels from thesecond subset may also belong to the first subset. In one instance, theinstructions determine the pixel identifier value for each pixel fromthe third subset of the plurality of pixels by receiving the sensedinformation for a plurality of sensing environments. In certain aspects,the plurality of pixels belonging to the second subset may be receivedby the device coupled to the sensor from a remote device.

According to certain aspects, an example method for authenticating acomputing device may include, receiving, at a first computing device, afirst identifier for a sensor from a second computing device, whereinthe sensor is coupled to the second computing device, determining, atthe first computing device, a second identifier for the sensor using afirst variance associated with a first subset of pixels from theplurality of pixels for the sensor, a second variance associated with asecond subset of pixels from the plurality of pixels for the sensor andinformation associated with each of a third subset of pixels from theplurality of pixels, and determining, at the first computing device, ifthe first identifier and the second identifier both are associated withthe sensor by comparing the first identifier and the second identifier.

In some aspects of the example method, comparing the first identifierand the second identifier, for determining if the first identifier andthe second identifier are both associated with the sensor, may includedetermining a distance between the first identifier and the secondidentifier, and determining that the first identifier and the secondidentifier are both associated with the sensor if the distance isshorter than a threshold. In certain aspects, the plurality of pixelsfrom the third subset also belong to the first subset and the secondsubset and the second subset also belongs to the first subset. In someinstances, determining the pixel identifier value for each pixel fromthe third subset of the plurality of pixels comprises receiving thesensed information for a plurality of sensing environments. In oneaspect, the sensor is an ultrasonic sensor.

Example techniques, described herein, use variations in the sensor togenerate an identifier. Each sensor may be comprised of sub-sensingunits, called pixels, that may demonstrate variation in their sensingcapability from one pixel to another, due to, but not limited to, themanufacturing process, the variability of the materials used in theconstruction of the sensor, and the analog-to-digital conversionprocess. Examples of the teachings of the disclosure describe a methodfor using the relative variance associated with each pixel (relative tothe whole sensor or/and a portion of the sensor) in generating anidentifier for the sensor. In certain aspects, the method may obtaininformation associated with a plurality of pixels from a sensor, detectvariations in the information associated with each of the pixels from asubset of the plurality of pixels and generate an identifier for thesensor using the detected variations in the information associated witheach of the pixels from the subset of plurality of pixels.

The foregoing has outlined rather broadly features and technicaladvantages of examples in order that the detailed description thatfollows can be better understood. Additional features and advantageswill be described hereinafter. The conception and specific examplesdisclosed may be readily utilized as a basis for modifying or designingother structures for carrying out the same purposes of the presentdisclosure. Such equivalent constructions do not depart from the spiritand scope of the appended claims. Features which are believed to becharacteristic of the concepts disclosed herein, both as to theirorganization and method of operation, together with associatedadvantages, will be better understood from the following descriptionwhen considered in connection with the accompanying figures. Each of thefigures is provided for the purpose of illustration and description onlyand not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are illustrated by way of example. Thefollowing description is provided with reference to the drawings, wherelike reference numerals are used to refer to like elements throughout.While various details of one or more techniques are described herein,other techniques are also possible. In some instances, well-knownstructures and devices are shown in block diagram form in order tofacilitate describing various techniques.

A further understanding of the nature and advantages of examplesprovided by the disclosure may be realized by reference to the remainingportions of the specification and the drawings, wherein like referencenumerals are used throughout the several drawings to refer to similarcomponents. In some instances, a sub-label is associated with areference numeral to denote one of multiple similar components. Whenreference is made to a reference numeral without specification to anexisting sub-label, the reference numeral refers to all such similarcomponents.

FIG. 1 illustrates an example sensor comprising a plurality of pixels.

FIG. 2 illustrates an example of a pixel circuit.

FIG. 3 illustrates an example representation of the material layout ofan ultrasonic sensor.

FIG. 4 illustrates an example representation of analog-to-digitalconversion process for a sensor.

FIG. 5 illustrates a flow diagram for illustrating an example of aprocess for generating an identifier for a sensor.

FIGS. 6A, 6B, and 6C illustrate three different configurations for afirst subset of pixels, a second subset of pixels and a third subset ofpixels used in generating an identifier in some aspects of thedisclosure.

FIG. 7 illustrates an example process for generating a mean and standarddeviation for multiple scans of the sensor.

FIG. 8 illustrates an example process for generating a mean and standarddeviation for a portion of the sensor.

FIG. 9 illustrates an example representation of the identifier generatedusing pixel identifier values associated with a plurality of pixels.

FIG. 10 illustrates a block diagram according to one or more aspects ofthe computing device coupled to the sensor.

FIG. 11 illustrates a flow diagram for performing a method according toone or more aspects of the disclosure, as performed by an authenticationcomputing device.

FIG. 12 illustrates a block diagram according to one or more aspects ofthe authentication computing device.

FIG. 13 illustrates another flow diagram for illustrating an example ofa process for generating an identifier for a sensor.

FIG. 14 illustrates an example of a computing device for implementingone or more aspects of the disclosure.

DETAILED DESCRIPTION

Several illustrative embodiments will now be described with respect tothe accompanying drawings, which form a part hereof While particularembodiments, in which one or more aspects of the disclosure may beimplemented, are described below, other embodiments may be used andvarious modifications may be made without departing from the scope ofthe disclosure or the spirit of the appended claims.

Techniques described herein provide a method, system and apparatus forgenerating an identifier for a sensor. Sensors detect physical input andin some instances convert the physical input to electrical or opticaloutput. The electrical output may be used by a device hosting the sensorin a variety of ways. Some examples of sensors may include inertialsensors, imaging sensors, chemical sensors, biometric sensors,ultrasonic sensors, etc. Ultrasonic sensors may operate by interpretingthe echoes from radio or sound waves. For instance, ultrasonic sensorsmay generate high frequency sound waves and evaluate the echo which isreceived back by the sensor. In some implementations, ultrasonic sensorscalculate the time interval between sending the signal and receiving theecho to determine the distance to an incident surface. In someinstances, the ultrasonic sensors may also operate in a passive mode bydetecting ambient signals from the environment. One application ofultrasonic sensors may include detecting fingerprints of a user forauthenticating the user.

In some embodiments, the identifier for the sensor may refer to a stringof bits that uniquely (or unique within an acceptable degree) identifiesthe sensor. In some instances, uniquely identifying the sensor mayincrease or augment the security of the authentication process. Uniquelyidentifying the sensor may allow systems, remote servers, clouds,applications and programs to improve security and also enable forensicsin instances of security breaches, in some instances. For example, insome instances, it may be useful for a backend system to ascertain thata user fingerprint was acquired using a specific sensor.

Some current solutions provide fixed identifiers, in some instances,etched into the sensor. However, these identifiers are inflexible,expensive to implement and can be faked, masked, changed or stolen.Techniques described herein provide a cost effective and robust methodfor identifying a sensor.

In certain embodiments of the invention, techniques describe a methodfor generating an identifier for the sensor using intrinsic propertiesof the sensor. Described techniques allow generation of an identifier ina cost effective manner using spatially temporal and global informationfrom the sensor that is robust against contrast variations, input signalvariations, and gradual changes of sensor characteristics. Furthermore,techniques described herein allow for using an identifier for a sensoreven in instances where the sensors have defects and degradations.

In one embodiment, techniques described use variations in the sensor togenerate an identifier. FIG. 1 illustrates an example sensor 100comprising one or more pixels. In some instances, a “pixel” may also bereferred to as a “pixel circuit” and used interchangeably withoutdeparting from the scope of the invention. Pixels may be sub-sensingunits within the sensor. In FIG. 1, the illustration of the sensor 100represents 64 (8×8) pixels in the sensor. In various implementations,the shape of the sensor and the pixels, the number of pixels and thespacing between the pixels may vastly vary, without departing from thescope of the invention. Pixel blocks 102 represent two example pixelsfrom a grid of 64 pixels.

FIG. 2 illustrates an example of a pixel 200 shown in FIG. 1. Each pixelof the sensor may be capable of sensing and may be constructed using oneor more transistors, diodes and resistors. An example of a pixel is athin-film transistor (TFT) pixel circuit. In some implementations, anultrasonic sensor may use a plurality of TFT pixel circuits.

In one example implementation, the pixel may receive an alternativecurrent (AC) signal 202 and a direct current (DC) signal 204. In someimplementations, the pixel 200 may receive only the AC signal 202, onlythe DC signal 204, both AC signal 202 and DC signal 204 or no signal atall. In an ultrasonic sensor, the current may be used for exciting wavesinside the sensor. The ultrasonic sensor may sense the echo which isreceived back by the sensor. In some implementations, ultrasonic sensorscalculate the time interval between sending the signal and receiving theecho to determine the distance to an incident surface. In someinstances, the ultrasonic sensors may also operate with little or nocurrent and operate in a passive mode by detecting ambient signals fromthe environment.

The output signal 206 may indicate the result of the sensing performedby the sensor. For example, the output signal 206 may output a currentand at a particular voltage. In some instances, the output signal 206may be interpreted as an analog signal that may be further digitizedusing an analog-to-digital converter (ADC) circuit based on the currentand/or the voltage level of the output signal 206. An example of an ADCis described in more detail in FIG. 4. In some aspects, the outputsignal 206 for the various pixels may vary for the same AC signal 202,DC signal 204, or stimulus (e.g., finger present or not present) due toinherent differences in the pixels.

Embodiments of the invention use the variation associated with theindividual pixels from the sensor in generating an identifier for thesensor. In some embodiments, the detected variation is measured relativeto the variation of a part of the sensor or/and the entire sensor ingenerating the identifier for the sensor. Using relative measurementsallows for gradual changes of the sensor and even minor damage to thesensor (i.e., dead pixels) without losing the ability to uniquelyidentify the sensor.

Variations in sensing of the individual pixels may be introduced due toa variety of reasons. For example, variations may be introduced throughthe manufacturing process of the circuit that includes several differentcomponents, such as the transistors, diodes and resistors. Inmanufacturing, due to non-ideal manufacturing processes, each pixelcircuit or a group of pixel circuits may be different from another pixelcircuit or group of pixels of the sensor.

Similarly, variations in the different materials over a contiguous ornon-contiguous region of the materials used in the construction of thesensor may also affect the sensing capabilities of each pixel or groupof pixels. For example, FIG. 3 illustrates an example representation ofthe layout of an ultrasonic sensor 300. The ultrasonic sensor 300 fromFIG. 3 is constructed using a TFT substrate 306 comprising TFT pixelsand various adhesives, air gaps, metal layers, glass layers, etc. Eachof these layers inadvertently has (or “may have”) variations whenexamined over a contiguous region and may result in variations in thesensing capability of each pixel or group of pixels. In addition, inlow-cost manufacturing processes, there could be air bubbles in some ofthe materials, which would also result in variations in the signaldetection capabilities for the pixels affected. As described inembodiments of the invention, such variations in the sensing of thepixels may result in varying response (i.e., output signal 304) for aninput signal 302 and may be used in generating the identifier for thesensor.

FIG. 4 illustrates an example representation of an analog-to-digitalconverter (ADC) 400 that illustrates the analog-to-digital conversionprocess for a sensor. The blocks depicted in FIG. 4 may represent someof the components of an example ADC 400, but embodiments of theinvention are not limited by such a representation. Theanalog-to-digital process may also introduce some variations for eachpixel or group of pixels. For example, the analog-to-digital conversionprocess may process sensor output analog signal 402 from a number ofpixels (i.e., output signal 206) through the same circuit and generate adigital signal 410. In some embodiments, the same circuit or applicationspecific integrated circuit (ASIC) may be used in the ADC process formultiple pixels. In one implementation, a multiplexer (i.e., MUX) 404may be used for selecting the signals from the appropriate pixelcircuit. The process of selecting the signals in the MUX 400 itself mayintroduce variations in the final sensing capability for a pixel. Forexample, cross-noise between the selecting signal and the signals in theMUX 400 may vary based on the signal selected. Furthermore, the signalfrom each pixel may have a slightly different route compared to theother signals leading to variations in the detecting of the signal. Thecircuitry for the filter 406 and the A/D 408 components may alsointroduce additional variations. As described in embodiments of theinvention, such variations in the sensing of the pixels may be used ingenerating the identifier for the sensor.

Example variations described above are relatively quite stable over timefor the same sensor. However, they may be different from other seeminglyidentical sensors produced even using the same manufacturing process. Inother words, each sensor has its unique pixel variation.

Embodiments of the invention provide a method for generating anidentifier using such detected variations for each pixel or a group ofpixels. In one example embodiment, an ultrasonic sensor may bediscussed. However, embodiments of the invention are not limited to anultrasonic sensor and may be used with various other sensors.

FIG. 5 illustrates a flow diagram for performing a method for generatingan identifier for a sensor, according to one or more embodiments of theinvention. According to one or more aspects, any and/or all of themethods and/or method steps described in the flow diagram 500illustrated in FIG. 5 may be implemented by and/or by a computingdevice, such as a mobile device. Illustrative but non-limitingcomponents of such a computing device are described in greater detail inFIG. 14. In one embodiment, one or more of the method steps describedbelow with respect to FIG. 5 are implemented by a processor or anapplication-specific integrated circuit (ASIC) of the mobile device,such as the processor 1410 or another processor. Additionally oralternatively, any and/or all of the methods and/or method stepsdescribed herein may be implemented in computer-readable instructions,such as computer-readable instructions stored on a computer-readablemedium such as the memory 1435, storage 1425 or another computerreadable medium.

In certain embodiments, multiple bits may be used to represent thevariation associated with each pixel relative to other pixels andvarious sensing environments. In some instances, each bit may representa different sensing environment associated with the same pixel. Thereliability of the representation of the variability of the pixel may beincreased by determining the variability of the pixel over a greaternumber of sensing environments.

For illustration purposes, in an example setting that uses an ultrasonicsensor, three different sensing environments may be selected. In thefirst example sensing environment (BG1) for the ultrasonic sensor, anormal DC bias with the tone burst generator disabled may be used. Inthe second example sensing environment (BG2) for the ultrasonic sensor,a normal DC bias with the tone burst generator enabled may be used. Inthe third example sensing environment (BG3) for the ultrasonic sensor, anormal DC bias shifted by 0.1 V with the tone burst generator disabledmay be used. In one implementation, for the ultrasonic fingerprintsensor, the sensing may be performed without a finger present on theultrasonic sensor.

The sensing environment may be selected based on the sensor type. Forexample, for a camera, the sensing environments may include sensing withno light, sensing with white light and sensing with red light.

At block 502, components of the computing device may access sensedinformation for each pixel from a plurality of pixels of the sensor foran at least one sensing environment. Sensed information may refer to ananalog or digital signal detected for a sensor subjected to a particularsensing environment. In certain other embodiments, the method performs ascan of the sensor and accesses sensed information for each of the abovedescribed sensing environments to determine the measurement for eachpixel under the different sensing environments.

In certain embodiments, multiple scans for the same sensing environmentfor the same pixels may be performed to normalize the data collectedover multiple iterations. Performing multiple scans may increase thereliability of the data. Normalization of the data may be performedusing a simple mean or a medium calculation over multiple iterations(N₁, N₂ and N₃). Following is an example equation representing threedatasets for the absolute measurement values for the pixels for thesensors (A_(BG1), A_(BG2) and A_(BG3)) for the three different sensingenvironments (BG1, BG2 and BG3), respectively.

${A_{{BG}\; 1} = {\frac{1}{N_{1}}{\sum\limits_{i = 1}^{N_{1}}{{BG}\; 1_{i}}}}},{A_{{BG}\; 2} = {\frac{1}{N_{2}}{\sum\limits_{i = 1}^{N_{2}}{{BG}\; 2_{i}}}}},{{{and}\mspace{14mu} A_{{BG}\; 3}} = {\frac{1}{N_{3}}{\sum\limits_{i = 1}^{N_{3}}{{BG}\; 3_{i}}}}}$

At block 504, components of the computing device may determine a firstvariance representing a variation in the sensed information for a firstsubset of the plurality of pixels using the sensed information for eachpixel from the first subset of the plurality of pixels of the sensor.Blocks 602, 610 and 616 of FIGS. 6A, 6B and 6C, respectively, representexample subsets of pixels included in the first subset.

In one implementation, the first subset may refer to a global subsetcomprising sensed information for all of the pixels for the sensor. Insuch a scenario, the first variance may be referred to as a globalvariance. Such an implementation of the first subset may be depicted byblock 602 of FIG. 6A, where the first subset includes all of the pixelsof the sensor. However, as described in further detail below withrespect to FIG. 6B and FIG. 6C, in some implementations, the firstsubset may not comprise all of the pixels of the sensor.

In certain aspects, the data set A_(BG1) may include 64 different datapoints representing each pixel for the sensor 100 represented in FIG. 1.In one example, where the first subset represents a global subset andthe first variance refers to a global variance, a mean and standarddeviation (μ₁, σ₁), (μ₂, σ₂), and (μ₃, σ₃) may be calculated for eachdataset (A_(BG1), A_(BG2) and A_(BG3)) that may be used to represent theglobal variability of the sensor in their respective sensing environment(BG1, BG2 and BG3).

Briefly referring to FIG. 7, FIG. 7 illustrates the example process ofgenerating a mean and standard deviation for multiple scans of thesensor. For example, multiple (N₁) scans may be performed and averagedto generate a single dataset associated with the plurality of pixels fora sensing environment (A_(BG1)). The dataset may be further processed togenerate a mean and standard deviation to represent the variability ofthe first subset of pixels (global variance, where the first subsetincludes all the pixels of the sensor).

At block 506, components of the computing device may determine a secondvariance representing a variation in the sensed information for a secondsubset of the plurality of pixels using the sensed information for eachpixel from the second subset of the plurality of pixels of the sensor,wherein the first subset of the plurality of pixels is different fromthe second subset of the plurality of pixels. Blocks 604, 612 and 618 ofFIGS. 6A, 6B and 6C, respectively, represent example subsets of pixelsincluded in the second subset.

In certain implementations, the pixels included in the second subset aredetermined by a remote computing device, such as a remote server, thatmay request an identifier from the computing device coupled to thesensor. In certain other implementations, the computing device mayselect a plurality of pixels (or location/region of the pixels) to beincluded in the second subset. In certain implementations, the pixelsincluded in the second subset may be determined based on the design ofthe sensor or the ADC converter. For example, in one implementation, Mbits may be selected for the second subset based on the transmissionchannel shared by multiple pixel circuits.

Similar to block 504, a second variance may be determined for a regionof the sensor (second subset) using sensed information for those pixels.Determining multiple variances may provide the computing device, inblock 508, multiple points for comparison for any particular pixel forthe purpose of generating an identifier. At least in one implementation,all M pixels may be grouped together to calculate a second mean andsecond standard deviation ({tilde over (μ)}₁, {tilde over (σ)}₁),({tilde over (μ)}₂, {tilde over (σ)}₂), and ({tilde over (μ)}₃, {tildeover (σ)}₃).

Briefly referring to FIG. 8, FIG. 8 illustrates a similar process toFIG. 7, wherein the method generates a mean and standard deviation for aregion that is a subset of the entire sensor. For example, a smallregion as indicated in FIG. 8 by the rectangular box 802 may be selectedas the second subset from the dataset associated with the plurality ofpixels for a sensing environment (A_(BG1)). The dataset may be furtherprocessed to generate a mean and standard deviation to represent thevariability associated with the local region (local variability). Insome instances, the identifier may be generated using information fromthe second subset of pixels. In such instances, the second subset ofpixels may be referred to as the local subset and the second variancemay be referred to as the local variance.

At block 508, components of the computing device may determine a pixelidentifier value for each pixel from a third subset of the plurality ofpixels by comparing the sensed information for each pixel from the thirdsubset of the plurality of pixels with the first variance and the secondvariance. Blocks 606, 614 and 620 of FIGS. 6A, 6B and 6C, respectively,represent example subsets of pixels included in the third subset. In oneimplementation, the pixel identifier values may be a string of bits foreach pixel from the third subset of the plurality of pixels and may beused in generating the identifier.

For example, in one implementation, the computing device may compare themeasurements of the pixel to the first and second variances for eachsensing environment. In one implementation, if the absolute measurementor sensed information of the pixel relative to the first (or second)measurements falls within an acceptable range (based on the mean andstandard deviation), then a zero value may be assigned for the pixel forthat sensing environment, and vice versa. The above example settingyields six bits of information representing the relative variability foreach pixel, since there are three sensing environments (BG1, BG2 andBG3) and two groups of pixels (first and second subset) that therelativity of the current pixel is measured against. The followingequations represent example generation of the six bit pixel identifiervalue representing the variability of each pixel. α, β, γ, {tilde over(α)}, {tilde over (β)}, and {tilde over (γ)} are variables that may beused to tune the range of the acceptable variability from the mean ormedium.

-   -   First bit=0: if A_(BG1)(x, y)ε [μ₁−ασ₁, μ₁+ασ₁]        -   Otherwise, second bit=1.    -   Second bit=0: if A_(BG2)(x, y)ε [μ₂−βσ₂, μ₂+βσ₂]        -   Otherwise, second bit=1.    -   Third bit=0: if A_(BG3)(x, y)ε [μ₃−Δσ₃, μ₃+γσ₃]        -   Otherwise, third bit=1.    -   Fourth bit=0: if A_(BG1)(x, y)ε [{tilde over (μ)}₁−{tilde over        (α)}{tilde over (σ)}₁, {tilde over (μ)}₁+{tilde over (α)}{tilde        over (σ)}₁]        -   Otherwise, fourth bit=1.    -   Fifth bit=0: if A_(BG2)(x, y)ε [{tilde over (μ)}₂−{tilde over        (β)}{tilde over (σ)}₂, {tilde over (μ)}₂+{tilde over (β)}{tilde        over (σ)}₂]        -   Otherwise, fifth bit=1.    -   Sixth bit=0: if A_(BG3)(x, y)ε [{tilde over (μ)}₃−{tilde over        (γ)}{tilde over (σ)}₃, {tilde over (μ)}₃+{tilde over (γ)}{tilde        over (σ)}₃]        -   Otherwise, sixth bit=1.

At block 510, components of the computing device may generate theidentifier using the pixel identifier values for each of the pluralityof pixels from the third subset of the plurality of pixels. For example,as shown in FIG. 9, in one example, for X-by-Y pixels, 6XY bits for anidentifier may be generated. In one simplistic example, the pixelidentifier values for the plurality of pixels from the third subset maybe concatenated to generate the identifier.

It should be appreciated that the specific steps illustrated in FIG. 5provide a particular method of switching between modes of operation,according to an embodiment of the present invention. Other sequences ofsteps may also be performed accordingly in alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps/blocks outlined above in a different order. To illustrate, auser may choose to change from the third mode of operation to the firstmode of operation, the fourth mode to the second mode, or anycombination therebetween. Moreover, the individual steps/blocksillustrated in FIG. 5 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps/blocks may be added or removed dependingon the particular applications. One of ordinary skill in the art wouldrecognize and appreciate many variations, modifications, andalternatives of the process.

FIGS. 6A, 6B and 6C illustrate example variations of pixels included ina first subset, second subset and third subset from the plurality ofpixels for a sensor. FIGS. 6A, 6B and 6C represent only a few differentconfigurations for generating an identifier and embodiments of theinvention are not limited by these configurations.

For example, in FIG. 6A, the first subset 602 includes all the pixels ofthe sensor and represents a global set. The second subset 604 representsa set different from the first subset 602, even though the pixelsincluded in the second subset 604 are also included in the first subset602. Since, the second subset 604 is different from the first subset602, the converse is not true (i.e., the second subset 604 does notinclude all the pixels from the first subset 602). As shown in FIG. 6A,the pixels included in the third subset 606 are also included in thesecond subset 604. In one instance, the second subset 604 and the thirdsubset 606 can be the same. When the second subset 604 and the thirdsubset 606 are the same, the identifier is generated using pixel valueidentifiers for each pixel from the second/third subset 604.

FIG. 6B illustrates an example where the first subset 610 of pixels doesnot include all of the pixels from the sensor. Furthermore, in FIG. 6B,all the pixels from the second subset 612 are not included in the firstsubset 610. As shown in FIG. 6B, the pixels from the third subset 614are included in the first subset 610 and the second subset 612 ofpixels.

FIG. 6C illustrates yet another example configuration, where the firstsubset 616, the second subset 618 and the third subset 620 are alldistinct subsets without any overlap in pixels.

Several such configurations can be constructed without departing fromthe scope of the invention. Selecting several such configurations,wherein the scope of each subset is variable in terms of coverageregions and the number of pixels, allows the computing device togenerate a large number of different and sufficiently unique identifiersassociated with the same sensor. In some implementations, in addition toa first subset and a second subset, additional subsets may be definedand used for generating multiple variances. Therefore, embodiments ofthe invention are not limited in scope to two variances and may usemultiple variances for generating the identifier.

A second computing device, such as a trusted backend server, may alsogenerate an identifier using the same configuration parameters used bythe sensor in generating the identifier. By comparing the identifiergenerated by the computing device and the identifier generated locally,the second computing device can uniquely identify and/or authenticatethe sensor used in the computing device.

In some aspects, the configuration for generating the identifier may bepre-negotiated between the two computing devices. In other aspects, theconfiguration for generating the identifier may be determined at thesecond computing device, such as the trusted backend server. In yetother aspects, the configuration for generating the identifier may bedetermined at the computing device coupled to the sensor.

In one example, the configuration information is determined and receivedfrom the second computing device, such as the trusted backend server. Inanother example, the configuration information may be determinedindependently by each of the two computing devices using a synchronizedtime stamp or shared seed/secret for a random number generator for thetwo devices.

The unique identifier may be useful to any (trusted or untrusted) remotedevice that may be interested in differentiating between multiplesensors. In addition, a backend server (such as a trusted server) mayalso have sensed information for each of the pixels for the sensor forthe different sensing environments and the configuration used forgenerating the identifier by the computing device coupled to the sensor.Such a backend server may also generate the identifier and authenticatethe sensor (i.e., determine not only that the sensor associated with theidentifier is unique, but also that the sensor associated with theidentifier is a particular sensor known (directly or indirectly) to thebackend server).

FIG. 10 illustrates a block diagram for generating an identifier for asensor by a computing device coupled to the sensor. The computing devicemay be a computing device implemented using one or more componentsdescribed in FIG. 14. Modules described in FIG. 10 may be implementedusing software, firmware, hardware or any other combination thereof. Inone embodiment, some of the modules described in FIG. 10 may be storedas software modules on a computer-readable medium 1000 that may be anymagnetic, electronic, optical, or other computer-readable storagemedium. In one implementation, the computer-readable storage medium 1000may include an information receiver 1004, first variance generator 1006,second variance generator 1008, pixel identifier generator 1010,identifier generator 1012 and sensing environment controller 1014.

At block 1004, the information receiver 1004 module may receive sensedinformation from the sensor 1002. In one implementation, the informationreceiver 1004 module may receive information for each of the pixels or“pixel circuits” associated with the sensor 1002 and store the sensedinformation in memory 1435. In one implementation, the informationreceiver may receive information for several different sensingenvironments and store the information associated with the sensor fordifferent sensing environments in separate memory buffers.

In some implementations, the information receiver 1004 module mayreceive multiple iterations of information from the sensor 1002 for thesame sensing environment (controlled by the sensing environmentcontroller 1014 module). The information receiver 1004 module canaverage the data received over multiple iterations to reduce errors ortemporary fluctuations in the measurements or sensing of theinformation. In one implementation, the information receiver 1004 modulereceives information for all the pixels of the sensors for each andevery request for generation of a sensor identifier. In anotherimplementation, the information receiver 1004 refreshes the storedinformation for the sensors operating in different sensing environmentsperiodically and not on every request for generation of a sensoridentifier.

At block 1014, the sensing environment controller 1014 module may selectthe various different sensing environments for the sensor 1002 forretrieving the sensed information. For illustration purposes, in anexample setting that uses an ultrasonic sensor, three different sensingenvironments may be selected. In the first example, sensing environment(BG1) for the ultrasonic sensor, a normal dc bias with the tone burstgenerator disabled may be used. In the second example, sensingenvironment (BG2) for the ultrasonic sensor, a normal DC bias with thetone burst generator enabled may be used. In the third example, sensingenvironment (BG3) for the ultrasonic sensor, a normal DC bias shifted by0.1 V with the tone burst generator disabled, may be used.

At block 1006, the first variance generator 1006 module uses informationassociated with the first subset and generates a first variance. In oneimplementation, the first subset includes all of the pixels of thesensor and the first variance represents the global variance. In oneaspect, the first variance for a sensing environment may be generated bycalculating a mean of the sensed information for each of the pixelsbelonging to the first subset and the standard deviation for the pixelsbelonging to the first subset. The first variance generator 1006 modulemay receive the sensed information for the first subset of pixels fromthe information receiver 1004 module.

At block 1008, the second variance generator 1008 module usesinformation associated with the second subset and generates a secondvariance. In one implementation, the second subset is different from thefirst subset in at least one pixel. In one aspect, the second variancefor a sensing environment may be generated by calculating a mean of thesensed information for each of the pixels belonging to the second subsetand the standard deviation for the pixels belonging to the secondsubset. The second variance generator 1008 module may receive the sensedinformation for the second subset of pixels from the informationreceiver 1004 module.

Although the first variance generator 1006 and the second variancegenerator 1008 are discussed, embodiments of the invention are notlimited to generation of only two variances and several more variancesmay be generated in certain embodiments.

At block 1010, the pixel identifier value generator 1010 module maygenerate a value associated with a pixel that identifies the pixel. Inone aspect, the pixel identifier value generator 1010 module may selectone pixel from a third subset of pixels for generating the pixelidentifier value. The pixel identifier value generator 1010 module maycompare the sensed information for the pixel against the first variancegenerated by the first variance generator 1006 module to generate onebit of information. Similarly, the pixel identifier value generator 1010module may compare the sensed information for the same pixel against thesecond variance generated by the second variance generator 1008 moduleto generate a second bit of information. Similarly, if the firstvariance and the second variance are generated for several differentsensing environments, the pixel identifier value generator 1010 modulecan generate a bit of information for each of those sensingenvironments. For example, if three different sensing environments maybe configured by the sensing environment controller 1014 module, thensix different bits of information may be generated for a single pixelfrom the third subset.

The pixel identifier value generator 1010 module may repeat the sameprocess for each pixel from the third subset of pixels. At block 1012,the identifier generator module may combine the pixel identifier valuesfor each of the pixels from the third subset and generate an identifierfor the sensor 1002. In one implementation, the sensor identifier may besent to a device, such as a remote device using a communicationsubsystem 1016 similar to the communication subsystem 1430 described inFIG. 14.

FIG. 11 illustrates a flow diagram for performing a method, by anauthentication computing device, according to one or more embodiments ofthe invention. According to one or more aspects, any and/or all of themethods and/or method steps described in the flow diagram 1100illustrated in FIG. 11 may be implemented by and/or in a computingdevice. In one example, the computing device is a remote device, such asa trusted backend server that authenticates the identity of the sensor.In another example, the computing device is a secondary device orportable dongle with computing logic for establishing the authenticityof the sensor. Illustrative but non-limiting components of such acomputing device are described in greater detail in FIG. 14. In oneembodiment, one or more of the method steps described below with respectto FIG. 11 are implemented by a processor or an application specificintegrated circuit (ASIC) of the mobile device, such as the processor1410 or another processor. Additionally or alternatively, any and/or allof the methods and/or method steps described herein may be implementedin computer-readable instructions, such as computer-readableinstructions stored on a computer-readable medium such as the memory1435, storage 1425 or another computer readable medium.

At block 1102, components of an authentication computing device may beconfigured to receive (using a communications subsystem 1430) a firstidentifier associated with a sensor from a computing device, wherein thesensor is coupled to the computing device.

At block 1104, components of the authentication computing device maydetermine a second identifier for the sensor using a first varianceassociated with a first subset of pixels from the plurality of pixelsfor the sensor, a second variance associated with a second subset ofpixels from the plurality of pixels for the sensor and informationassociated with each of a third subset of pixels from the plurality ofpixels. The second identifier may be generated using information storedin the memory 1435 of the authentication computing device or a devicecoupled to the server computing device. In one implementation, during aprovisioning phase, the sensed information associated with the pixels ofthe sensors operating under different sensing environments may be storedon the server computing device or a device coupled to the firstcomputing device.

The process of generating the second identifier may be similar in someaspects to the process of generating the first identifier (describedwith reference to FIG. 5). The first subset, the second subset and thethird subset of pixels used in generating the identifier may bepre-negotiated between the authentication computing device and thecomputing device coupled to the sensor.

At block 1106, components of the authentication computing device maydetermine if the first identifier and the second identifier both areassociated with the same sensor by comparing the first identifier andthe second identifier. In certain embodiments, comparing the firstidentifier and the second identifier for determining if the firstidentifier and the second identifier are both associated with the samesensor may include determining a distance between the first identifierand the second identifier, and determining that the first identifier andthe second identifier are both associated with the sensor if thedistance is shorter than a threshold.

During the process of authentication or identification, in someimplementations, components of the authentication computing device mayuse a hamming distance algorithm in comparing the first identifierreceived by the server computing device (D1) against the secondidentifier generated by the authentication computing device (D2), asshown below.

$h = {\frac{1}{6{XY}}{\sum\left( {D_{1\mspace{14mu}}{XOR}\mspace{14mu} D_{2}} \right)}}$

In one implementation, if h is smaller than a matching threshold T, thesensor will be authenticated or identified as the same sensor associatedwith identifier D2. Otherwise, the sensor may not be authenticated oridentified as expected sensor. Use of the hamming distance algorithm (orany similar algorithm) allows for flexibility and variability in theidentifier that may be caused by minor defects in the sensor andvariance in measurements due to environmental noise.

Furthermore, the identification accuracy may be increased by creating amask for each sensor ID. For instance, the mask value at each pixel maybe set as “000000” for a defective pixel. Otherwise, the mask maydefault to “111111” for a six bit representation of a pixel. The hammingdistance algorithm may be revised from above as follows to account formasks:

$h = {\frac{= {\sum{\left( {D_{1}\mspace{14mu} {AND}\mspace{14mu} M_{1}} \right){{XOR}\left( {D_{2}\mspace{14mu} {AND}\mspace{14mu} M_{2}} \right)}}}}{\sum{M_{1}\mspace{14mu} {AND}\mspace{14mu} M_{2}}}.}$

In some embodiments, the sensor identifier may be encrypted beforetransmitting the identifier to a remote entity.

It should be appreciated that the specific steps illustrated in FIG. 11provide a particular method of switching between modes of operation,according to an embodiment of the present invention. Other sequences ofsteps may also be performed accordingly in alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps/blocks outlined above in a different order. To illustrate, auser may choose to change from the third mode of operation to the firstmode of operation, the fourth mode to the second mode, or anycombination therebetween. Moreover, the individual steps/blocksillustrated in FIG. 11 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps/blocks may be added or removed dependingon the particular applications. One of ordinary skill in the art wouldrecognize and appreciate many variations, modifications, andalternatives of the process.

FIG. 12 illustrates a block diagram for authenticating an identifier fora sensor by an authentication computing device. The authenticationcomputing device may be a computing device implemented using one or morecomponents described in FIG. 14. Modules described in FIG. 12 may beimplemented using software, firmware, hardware or any other combinationthereof. In one embodiment, some of the modules described in FIG. 12 maybe stored as software modules on a computer-readable medium 1200 thatmay be any magnetic, electronic, optical, or other computer-readablestorage medium. In one implementation, the computer-readable storagemedium 1200 may include a first identifier receiver 1204, a secondidentifier generator 1206, and a comparator 1208. The second identifiergenerator 1206 may include a first variance generator/retriever 1210, asecond variance generator 1212, a pixel identifier value generator 1214and an identifier generator 1216.

In some embodiments, during a provisioning phase, an authenticationcomputing device or a device coupled to the server computing device mayreceive sensed information associated with a sensor that is stored inmemory 1435 and used by the server computing device to authenticate thesensor. For example, in one embodiment, the information for a sensor maybe acquired during the manufacturing or testing phase of the sensor andstored and accessible by the authentication computing device.

At the time of authenticating the sensor, the communications subsystem1202 coupled to the authentication computing device may receive a firstidentifier associated with a sensor from a device coupled to the sensor,using a transceiver. At block 1204, the first identifier receiver 1204may receive the first identifier at the authentication computing deviceand store it in memory 1435.

The second identifier generator 1206 module may generate the secondidentifier using sensed information for the sensor stored at theauthentication computing device or a device coupled to theauthentication computing device. In one embodiment, the sensedinformation stored may include sensed information for a multiple sensingenvironments. The authentication computing device and the computingdevice coupled to the sensor may also have the same configurationinformation regarding the first subset, second subset and third subsetof pixels for generating the identifier for the sensor. Theconfiguration information may be determined by the server computingdevice, the device coupled to the sensor or a combination of the two.

Similar to what has been described with reference to FIG. 5, the firstvariance generator/retriever 1210 may generate the first variance usingthe sensed information for the first subset of pixels from the pluralityof pixels for the sensor. In one implementation, the first variance isgenerated by one or more processors 1410, by determining the mean andstandard deviation for the sensed information for a sensing environmentfor the pixels belonging to a the first subset. In certainimplementations, the first subset includes all of the pixels for thesensor. In certain aspects, the first variance is the global varianceand may be determined once and/or periodically refreshed and not uponeach and every authentication request.

At the second variance generator 1212 module, the authenticationcomputing device may generate a second variance using the sensedinformation for the second subset of pixels from the plurality of pixelsfor the sensor. In one implementation, the second variance is generatedby one or more processors 1410, by determining the mean and standarddeviation for the sensed information for a sensing environment for thepixels belonging to the second subset.

At the pixel identifier value generator 1214 module, the sensedinformation for each pixel from a third subset of pixels is comparedagainst the first variance and the second variance for each sensingenvironment to generate the pixel identifier values for the pixels fromthe third subset.

At the identifier generator 1216, the second identifier is generated byusing the pixel identifier values generated by the pixel identifiervalue generator 1214 module for the pixels for the third subset ofpixels. In one simple implementation, the pixel identifier values areconcatenated to form the second identifier value.

The comparator 1208 module compares the first identifier value receivedfrom the first identifier receiver 1204 module and the second identifiervalue received from the second identifier generator 1206 module anddetermines if the two identifier values refer to the same sensor. If thetwo identifier values are determined to refer to the same sensor module,the authentication process on the server computing device passes.

FIG. 13 illustrates a flow diagram for performing a method according toone or more embodiments of the invention. According to one or moreaspects, any and/or all of the methods, and/or method steps described inthe flow diagram 1300 illustrated in FIG. 13, may be implemented byand/or in an mobile device, components of which are described in greaterdetail in FIG. 14, for instance. In one embodiment, one or more of theblocks described below with respect to FIG. 13 are implemented by aprocessor or an ASIC of the mobile device, such as the processor 1410 oranother processor. Additionally or alternatively, any and/or all of themethods and/or method steps described herein may be implemented incomputer-readable instructions, such as computer-readable instructionsstored on a computer-readable medium such as the memory 1435, storage1425 or another computer readable medium.

At block 1302, components of the computing device may obtain informationassociated with a plurality of pixels from a sensor. In one embodiment,the sensor may be an image sensor. In another embodiment, the sensor maybe an ultrasound sensor. In yet another embodiment, the sensor may be anultrasound fingerprint sensor. In certain embodiments, the sensor may beused for authenticating a user using biometric information. In oneembodiment, a mean and standard deviation may be generated using theinformation associated with the plurality of pixels from the sensor forvarious sensing environments.

At block 1304, components of the computing device may detect variationsin the information associated with each of the pixels from a subset ofthe plurality of pixels. In one embodiment, the variation for each ofthe pixels is determined respective to the variations of the pluralityof pixels. In another embodiment, components of the invention detectintrinsic variations in the produced information associated for each ofthe pixels from one or more subsets of the plurality of pixels; if twomore subsets are used, they may or may not overlap but any two subsetsare not exactly the same.

At block 1306, components of the computing device may generate anidentifier for the sensor using the detected variations in theinformation associated with each of the pixels from the subset ofplurality of pixels. In one embodiment, generating the identifier forthe sensor may include calculating a variance for each of the pixelsfrom the subset of a plurality of pixels, and generating the identifierusing the variance associated with each of the pixels from the subset ofplurality of pixels. In another embodiment, components of the embodimentmay generate an identifier for the sensor using the detected intrinsicvariations in the produced information associated with each of thepixels from the subset(s) of plurality of pixels. Furthermore, in oneembodiment, generating the identifier value comprises concatenating thevariances for the each of the plurality of pixels to generate theidentifier. The variance for each of the pixels may be determined usingmultiple sensing environments for the sensor.

The variations in the sensing capability of the pixels may be caused bya variety of reasons that may include variation in the circuit for eachpixel, wherein the variation in the circuit may be introduced by themanufacturing process, variation in material distributions for andaround each pixel, air bubbles in the material distributions of eachpixel and selection and transmission logic in the ADC conversionprocess.

It should be appreciated that the specific steps illustrated in FIG. 13provide a particular method of switching between modes of operation,according to an embodiment of the present invention. Other sequences ofsteps may also be performed accordingly in alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps outlined above in a different order. To illustrate, a user maychoose to change from the third mode of operation to the first mode ofoperation, the fourth mode to the second mode, or any combinationtherebetween. Moreover, the individual steps illustrated in FIG. 13 mayinclude multiple sub-steps that may be performed in various sequences asappropriate to the individual step. Furthermore, additional steps may beadded or removed depending on the particular applications. One ofordinary skill in the art would recognize and appreciate manyvariations, modifications, and alternatives of the process.

The described techniques allow a sensor identifier computational methodfor ultrasound fingerprint sensors that is applicable to many types ofsensors. The method detects abnormality (or variability) of a pixelsensing capability relative to other pixels to generate the value forthat pixel. In one embodiment, the relative difference between the pixelto the global area (or larger area) and the relative difference betweenthe pixel to the local area (or a small area) may be used to determinevariability of the pixel. The difference may be classified into twocategories: within a pre-defined normal range or not within apre-defined normal range based the statistical analysis of the area. Insome embodiments, only one scan or image may be used to generate thisidentifier, or in other embodiments, multiple scans or images may beused to generate the identifier.

The described techniques also allow for sensor identifier generation toadapt to gradual changes of the sensor and even damages of the sensor.In one embodiment, this may be accomplished by using masks to mask outdefects and take the mask into account while determining the hammingdistance, as described above. This may still achieve highverification/authentication accuracy.

Moreover, even in instances where the sensor has gradual changes ordegradation over time, the identifier generated at the computing devicemay still match the identifier by a remote device, since the identifieris generated based on relative changes of the sensing capacity of apixel relative to other pixels and not as an absolute measurement forthe pixels.

Furthermore, the described techniques allow for generation of a flexibleidentifier, since an identifier may be generated using the entire sensorpixels, small area(s) of the sensors, and/or random discrete locationsof the sensors, as described in the various configurations depicted inFIGS. 6A, 6B and 6C. Such variation in the generation of identifiers fora sensor can be used for generating a very large number of sufficientlyunique identifiers that are associated with the sensor and can beauthenticated by a remote device, such as a remote trusted backendserver. Generation of identifiers in such large numbers can help thwartman-in-the middle attacks, since the computing device coupled to thesensor can continuously change the identifiers relayed by the computingdevice to a remote device.

Similarly, generation of such a large number of identifiers that areverifiable by a remote computing device also enables challenge responseapproaches and a one-time identifier approach and makes the randomsensor verification/authentication very secure. For example, the remoteserver may have sensed information for all the pixels of the sensor.Such sensed information may be provisioned during a provisioning phase.When performing on-line authentication, the remote server mayrequest/challenge the sensor (or computing device coupled to the sensor)for an identifier for a one-time selected configuration (comprisingfirst subset, second subset and third subset) or location of the sensor,and the sensor may generate the identifier bits for this configurationchallenge request and send the identifier for remoteauthentication/verification. One-time authentication/verificationcapability may greatly strengthen the security.

Embodiments of the invention may also allow for greater computationaland transmission efficiency. In one example, if a sensor has 20-by-20pixels, some implementations may have 400 pixels. If, each time, 100pixels were required to generate the one-time ID, the describedtechniques can generate over 2×10²⁵⁴ identifiers, providing manyone-time IDs for the sensor.

Furthermore, the described technique can generate an identifier ofvaried length for the same sensor at different times forverification/authentication, allowing the same sensor identifier toadapt to different security and authentication needs.

FIG. 14 illustrates an example computing device incorporating parts ofthe device employed in practicing embodiments of the invention. Acomputing device as illustrated in FIG. 14 may be incorporated as partof any computerized system, herein. For example, computing device 1400may represent some of the components of a mobile device. Examples of acomputing device 1400 include, but are not limited to, desktops,workstations, personal computers, supercomputers, video game consoles,tablets, smart phones, laptops, netbooks, or other portable devices.FIG. 14 provides a schematic illustration of one embodiment of acomputing device 1400 that may perform the methods provided by variousother embodiments, as described herein, and/or may function as the hostcomputing device, a remote kiosk/terminal, a point-of-sale device, amobile multifunction device, a set-top box and/or a computing device.FIG. 14 is meant only to provide a generalized illustration of variouscomponents, any or all of which may be utilized as appropriate. FIG. 14,therefore, broadly illustrates how individual system elements may beimplemented in a relatively separated or relatively more integratedmanner.

The computing device 1400 is shown comprising hardware elements that maybe electrically coupled via a bus 1405 (or may otherwise be incommunication, as appropriate). The hardware elements may include one ormore processors 1410, including without limitation one or moregeneral-purpose processors and/or one or more special-purpose processors(such as digital signal processing chips, graphics accelerationprocessors, and/or the like); one or more input devices 1415, which mayinclude without limitation a camera, sensors 1450, a mouse, a keyboardand/or the like; and one or more output devices 1420, which may includewithout limitation a display unit, a printer and/or the like. Sensorsmay include ultrasonic sensors and/or other imaging sensors.

The computing device 1400 may further include (and/or be incommunication with) one or more non-transitory storage devices 1425,which may comprise, without limitation, local and/or network accessiblestorage, and/or may include, without limitation, a disk drive, a drivearray, an optical storage device, a solid-form storage device such as arandom access memory (“RAM”) and/or a read-only memory (“ROM”), whichmay be programmable, flash-updateable and/or the like. Such storagedevices may be configured to implement any appropriate data storage,including without limitation, various file systems, database structures,and/or the like.

The computing device 1400 might also include a communications subsystem1430. The communications subsystem 1430 may include a transceiver forreceiving and transmitting data or a wired and/or wireless medium. Thecommunications subsystem 1430 may also include without limitation amodem, a network card (wireless or wired), an infrared communicationdevice, a wireless communication device and/or chipset (such as aBluetooth™ device, an 802.11 device, a WiFi device, a WiMax device,cellular communication facilities, etc.), and/or the like. Thecommunications subsystem 1430 may permit data to be exchanged with anetwork (such as the network described below, to name one example),other computing devices, and/or any other devices described herein. Inmany embodiments, the computing device 1400 will further comprise anon-transitory working memory 1435, which may include a RAM or ROMdevice, as described above.

The computing device 1400 may comprise software elements, shown as beingcurrently located within the working memory 1435, including an operatingsystem 1440, device drivers, executable libraries, and/or other code,such as one or more application programs 1445, which may comprisecomputer programs provided by various embodiments, and/or may bedesigned to implement methods, and/or configure systems, provided byother embodiments, as described herein. Merely by way of example, one ormore procedures described with respect to the method(s) discussed abovemight be implemented as code and/or instructions executable by acomputer (and/or a processor within a computer); in an aspect, then,such code and/or instructions may be used to configure and/or adapt ageneral purpose computer (or other device) to perform one or moreoperations in accordance with the described methods.

A set of these instructions and/or code might be stored on acomputer-readable storage medium, such as the storage device(s) 1425described above. In some cases, the storage medium might be incorporatedwithin a computing device, such as computing device 1400. In otherembodiments, the storage medium might be separate from a computingdevice (e.g., a removable medium, such as a compact disc), and/orprovided in an installation package, such that the storage medium may beused to program, configure and/or adapt a general purpose computer withthe instructions/code stored thereon. These instructions might take theform of executable code, which is executable by the computing device1400 and/or might take the form of source and/or installable code,which, upon compilation and/or installation on the computing device 1400(e.g., using any of a variety of generally available compilers,installation programs, compression/decompression utilities, etc.) thentakes the form of executable code.

Substantial variations may be made in accordance with specificrequirements. For example, customized hardware might also be used,and/or particular elements might be implemented in hardware, software(including portable software, such as applets, etc.), or both. Further,connection to other computing devices 1400 such as network input/outputdevices may be employed.

Some embodiments may employ a computing device (such as the computingdevice 1400) to perform methods in accordance with the disclosure. Forexample, some or all of the procedures of the described methods may beperformed by the computing device 1400 in response to processor 1410executing one or more sequences of one or more instructions (which mightbe incorporated into the operating system 1440 and/or other code, suchas an application program 1445) contained in the working memory 1435.Such instructions may be read into the working memory 1435 from anothercomputer-readable medium, such as one or more of the storage device(s)1425. Merely by way of example, execution of the sequences ofinstructions contained in the working memory 1435 might cause theprocessor(s) 1410 to perform one or more procedures of the methodsdescribed herein.

The terms “machine-readable medium” and “computer-readable medium,” asused herein, refer to any medium that participates in providing datathat causes a machine to operate in a specific fashion. In an embodimentimplemented using the computing device 1400, various computer-readablemedia might be involved in providing instructions/code to processor(s)1410 for execution and/or might be used to store and/or carry suchinstructions/code (e.g., as signals). In many implementations, acomputer-readable medium is a physical and/or tangible storage medium.Such a medium may take many forms, including, but not limited to,non-volatile media, volatile media, and transmission media. Non-volatilemedia include, for example, optical and/or magnetic disks, such as thestorage device(s) 1425. Volatile media include, without limitation,dynamic memory, such as the working memory 1435. Transmission mediainclude, without limitation, coaxial cables, copper wire and fiberoptics, including the wires that comprise the bus 1405, as well as thevarious components of the communications subsystem 1430 (and/or themedia by which the communications subsystem 1430 provides communicationwith other devices). Hence, transmission media may also take the form ofwaves (including without limitation radio, acoustic and/or light waves,such as those generated during radio-wave and infrared datacommunications). In an alternate embodiment, event-driven components anddevices, such as cameras, may be used, where some of the processing maybe performed in analog domain.

Common forms of physical and/or tangible computer-readable mediainclude, for example, a floppy disk, a flexible disk, hard disk,magnetic tape, or any other magnetic medium, a CD-ROM, any other opticalmedium, punchcards, papertape, any other physical medium with patternsof holes, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory chip orcartridge, a carrier wave as described hereinafter, or any other mediumfrom which a computer may read instructions and/or code.

Various forms of computer-readable media may be involved in carrying oneor more sequences of one or more instructions to the processor(s) 1410for execution. Merely by way of example, the instructions may initiallybe carried on a magnetic disk and/or optical disc of a remote computer.A remote computer might load the instructions into its dynamic memoryand send the instructions as signals over a transmission medium to bereceived and/or executed by the computing device 1400. These signals,which might be in the form of electromagnetic signals, acoustic signals,optical signals and/or the like, are all examples of carrier waves onwhich instructions may be encoded, in accordance with variousembodiments of the invention.

The communications subsystem 1430 (and/or components thereof) generallywill receive the signals, and the bus 1405 then might carry the signals(and/or the data, instructions, etc. carried by the signals) to theworking memory 1435, from which the processor(s) 1410 retrieves andexecutes the instructions. The instructions received by the workingmemory 1435 may optionally be stored on a non-transitory storage device1425 either before or after execution by the processor(s) 1410.

The methods, systems, and devices discussed above are examples. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods described may be performed in an order different from thatdescribed, and/or various stages may be added, omitted, and/or combined.Also, features described with respect to certain embodiments may becombined in various other embodiments. Different aspects and elements ofthe embodiments may be combined in a similar manner. Also, technologyevolves and, thus, many of the elements are examples that do not limitthe scope of the disclosure to those specific examples.

Specific details are given in the description to provide a thoroughunderstanding of the embodiments. However, embodiments may be practicedwithout these specific details. For example, well-known circuits,processes, algorithms, structures, and techniques have been shownwithout unnecessary detail in order to avoid obscuring the embodiments.This description provides example embodiments only, and is not intendedto limit the scope, applicability, or configuration of the invention.Rather, the preceding description of the embodiments will provide thoseskilled in the art with an enabling description for implementingembodiments of the invention. Various changes may be made in thefunction and arrangement of elements without departing from the spiritand scope of the invention.

Also, some embodiments were described as processes depicted as flowdiagrams or block diagrams. Although each may describe the operations asa sequential process, many of the operations may be performed inparallel or concurrently. In addition, the order of the operations maybe rearranged. A process may have additional steps not included in thefigure. Furthermore, embodiments of the methods may be implemented byhardware, software, firmware, middleware, microcode, hardwaredescription languages, or any combination thereof. When implemented insoftware, firmware, middleware, or microcode, the program code or codesegments to perform the associated tasks may be stored in acomputer-readable medium such as a storage medium. Processors mayperform the associated tasks.

Having described several embodiments, various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the disclosure. For example, the above elements may merely bea component of a larger system, wherein other rules may take precedenceover or otherwise modify the application of the invention. Also, anumber of steps may be undertaken before, during, or after the aboveelements are considered. Accordingly, the above description does notlimit the scope of the disclosure.

What is claimed is:
 1. A method for generating an identifier for a sensor, comprising: accessing, by a computing device, sensed information for each pixel from a plurality of pixels of the sensor for an at least one sensing environment; determining, by the computing device, a first variance representing a variation in the sensed information for a first subset of the plurality of pixels using the sensed information for each pixel from the first subset of the plurality of pixels of the sensor; determining, by the computing device, a second variance representing a variation in the sensed information for a second subset of the plurality of pixels using the sensed information for each pixel from the second subset of the plurality of pixels of the sensor, wherein the first subset of the plurality of pixels is different from the second subset of the plurality of pixels; determining, by the computing device, a pixel identifier value for each pixel from a third subset of the plurality of pixels by comparing the sensed information for each pixel from the third subset of the plurality of pixels with the first variance and the second variance; and generating, by the computing device, the identifier using the pixel identifier values for each of the plurality of pixels from the third subset of the plurality of pixels.
 2. The method of claim 1, wherein the plurality of pixels from the third subset also belong to the first subset and the second subset.
 3. The method of claim 1, wherein the plurality of pixels from the second subset also belong to the first subset.
 4. The method of claim 1, further comprising determining the pixel identifier value for each pixel from the third subset of the plurality of pixels by receiving the sensed information for a plurality of sensing environments.
 5. The method of claim 1, wherein the at least one sensing environment is one or more of sensing configurations comprising the bias current enabled, bias current disabled, bias current shifted, tone burst enabled, and tone burst disabled.
 6. The method of claim 1, wherein generating the identifier value comprises concatenating the pixel identifier values for the plurality of pixels from the third subset of the plurality of pixels.
 7. The method of claim 1, wherein the plurality of pixels belonging to the second subset is received by the computing device coupled to the sensor from a remote device.
 8. The method of claim 1, wherein the sensor is an image sensor.
 9. The method of claim 1, wherein the sensor is an ultrasonic sensor.
 10. The method of claim 1, wherein the sensor is an ultrasonic fingerprint sensor.
 11. The method of claim 1, wherein the identifier is a one-time sensor identifier.
 12. A device for generating an identifier for a sensor, comprising: the sensor coupled to the device, the sensor comprising a plurality of pixels configured to sense information; a memory; a processor coupled to the memory and configured to: receive the sensed information for each pixel from the plurality of pixels of the sensor for an at least one sensing environment; determine a first variance representing a variation in the sensed information for a first subset of the plurality of pixels using the sensed information for each pixel from the first subset of the plurality of pixels of the sensor; determine a second variance representing a variation in the sensed information for a second subset of the plurality of pixels using the sensed information for each pixel from the second subset of the plurality of pixels of the sensor, wherein the first subset of the plurality of pixels is different from the second subset of the plurality of pixels; determine a pixel identifier value for each pixel from a third subset of the plurality of pixels by comparing the sensed information for each pixel from the third subset of the plurality of pixels with the first variance and the second variance; and generate the identifier using the pixel identifier values for each of the plurality of pixels from the third subset of the plurality of pixels.
 13. The device of claim 12, wherein the plurality of pixels from the third subset also belong to the first subset and the second subset.
 14. The device of claim 12, wherein the plurality of pixels from the second subset also belong to the first subset.
 15. The device of claim 12, further comprising determining the pixel identifier value for each pixel from the third subset of the plurality of pixels by receiving the sensed information for a plurality of sensing environments.
 16. The device of claim 12, wherein the at least one sensing environment is one or more of sensing configurations comprising the bias current enabled, bias current disabled, bias current shifted, tone burst enabled, and tone burst disabled.
 17. The device of claim 12, wherein generating the identifier value comprises concatenating the pixel identifier values for the plurality of pixels from the third subset of the plurality of pixels.
 18. The device of claim 12, wherein the plurality of pixels belonging to the second subset is received by the device coupled to the sensor from a remote device.
 19. The device of claim 12, wherein the sensor is an ultrasonic fingerprint sensor.
 20. The device of claim 12, wherein the identifier is a one-time sensor identifier.
 21. A non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium comprises instructions executable by a processor, the instructions comprising instructions to: receive sensed information for each pixel from a plurality of pixels of a sensor for an at least one sensing environment; determine a first variance representing a variation in the sensed information for a first subset of the plurality of pixels using the sensed information for each pixel from the first subset of the plurality of pixels of the sensor; determine a second variance representing a variation in the sensed information for a second subset of the plurality of pixels using the sensed information for each pixel from the second subset of the plurality of pixels of the sensor, wherein the first subset of the plurality of pixels is different from the second subset of the plurality of pixels; determine a pixel identifier value for each pixel from a third subset of the plurality of pixels by comparing the sensed information for each pixel from the third subset of the plurality of pixels with the first variance and the second variance; and generate the identifier using the pixel identifier values for each of the plurality of pixels from the third subset of the plurality of pixels.
 22. The non-transitory computer-readable storage medium of claim 21, wherein the plurality of pixels from the third subset also belong to the first subset and the second subset.
 23. The non-transitory computer-readable storage medium of claim 21, wherein the plurality of pixels from the second subset also belong to the first subset.
 24. The non-transitory computer-readable storage medium of claim 21, further comprising determining the pixel identifier value for each pixel from the third subset of the plurality of pixels by receiving the sensed information for a plurality of sensing environments.
 25. The non-transitory computer-readable storage medium of claim 21, wherein the plurality of pixels belonging to the second subset is received by the device coupled to the sensor from a remote device.
 26. A method for authenticating a computing device, comprising: receiving, at a first computing device, a first identifier for a sensor from a second computing device, wherein the sensor is coupled to the second computing device; determining, at the first computing device, a second identifier for the sensor using a first variance associated with a first subset of pixels from the plurality of pixels for the sensor, a second variance associated with a second subset of pixels from the plurality of pixels for the sensor and information associated with each of a third subset of pixels from the plurality of pixels; and determining, at the first computing device, if the first identifier and the second identifier both are associated with the sensor by comparing the first identifier and the second identifier.
 27. The method of claim 26, wherein comparing the first identifier and the second identifier, for determining if the first identifier and the second identifier are both associated with the sensor, comprises: determining a distance between the first identifier and the second identifier; and determining that the first identifier and the second identifier are both associated with the sensor if the distance is shorter than a threshold.
 28. The method of claim 26, wherein the plurality of pixels from the third subset also belong to the first subset and the second subset and the second subset also belongs to the first subset.
 29. The method of claim 26, further comprising determining the pixel identifier value for each pixel from the third subset of the plurality of pixels by receiving the sensed information for a plurality of sensing environments.
 30. The method of claim 26, wherein the sensor is an ultrasonic sensor. 